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Repair and disassembly information for amplifiers in home audio systems.

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I have a Sansui 550 Classique amplifier -need help

My Sansui 550 Classique amp will not turn on, just humming sound and we have blown multiple fuses. Now even when replacing the fuse we get nothing.

We’ve checked the speaker wires. Receiver turns on. Amp shorts out after a crackle-hum sound.

any advice for repairing this?

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thanks for the advice…quick question:

I haven’t opened up the amp yet and have never done this before, so, how do I tell which capacitors are bad? or are you recommending to replace them all? is there some type of tester I should get?

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@nancyallen If some of them are bad, there's a good chance that even if the others are okay right now, they will die soon.

As a general rule of thumb, I would replace them all.

There are testers for capacitors (some test the capacitance, and others test the internal resistance, but neither always are out of spec for them to be bad)

I'm assuming you know how to solder (and desolder components) if you're considering opening it.

Also be careful by any large capacitors, they should be discharged before desoldering, which can be done by connecting both terminals to a low value resistor with two wires attached. Something like 10 ohms should do the trick.

Hope that helps, and I hope your repair goes well!

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If it’s a pretty old amp (which it is), there’s a good chance some of the capacitors in the power circuit (and likely everywhere inside) have gone bad. This will cause it to not turn on, and in some cases draw too much power.
What you can do is open it, and then desolder all of the capacitors (making a table to note where they go based on their values, (eg. C16 might be 470uF 35V) and then go on somewhere like Digikey or Mouser and find the capacitors you need with their part search tool.
Once you replace them the problem should be fixed! Also, absolutely make sure to put the capacitors in the board with the correct polarity. Not doing this will make them explode.
Additionally, you should only have to replace capacitors that are of the aluminum electrolytic variety, so any ceramic ones can stay, etc…

I would recommend getting capacitors from Würth or Nichicon, but if you have to get them from other manufacturers due to stock shortages, that’s okay.

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Nancy S Allen さん、ありがとうございました!
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